Tracking Control of Underactuated Surface Ships: Using Unscented Kalman Filter to Estimate the Uncertain Parameters

This paper proposes an unscented Kalman filter (UKF) based tracking controller to force underactuated nonlinear autonomous ships to follow a reference path under constant disturbances induced by wave, wind and ocean-current. The controller development is based on UKF and backstepping techniques. The UKF is used to update the estimation of the uncertain parameters online to avoid the parameters´ drift due to time-varying added mass matrices. Along the way of tracking control, we obtain a new stability result for nonlinear underactuated systems with non-vanishing uncertainties. Simulations conducted with respect to the tracking control of unmanned ship illustrate the effectiveness of our proposed controller.